Skip to content


ai  101  pytorch  classification  nvidia  cuda  install  tensorrt  yolo  ardupilot  None  ros2  dds  micro ros  xrce  sitl  plugin  SITL  debug  rangefinder  pymavlink  mavros  gazebo  distance sensor  system_time  timesync  cmake  gtest  ctest  cpp  c++  format  fmt  multithreading  spdlog  camera  coordinate system  orb  matching  opencv  build  transformation  computer vision  homography  optical flow  of  trackers  cv  cyclonedds  eprosima  fastdds  simulation  config  ignition  bridge  sdf  tips  ign-transport  sensors  lidar  aptly  apt  encryption  pgp  docker  git  bundle  github  hooks  pre-commit  lxd  container  lxc  x11  profile  vscode  marpit  presentation  marp  markdown  mermaid  video  ffmpeg  gstreamer  cheat-sheet  sdp  v4l2loopback  gi  snippets  cheat Sheet  python  asyncio  future  click  cli  numpy  project  template  black  isort  docs  project document  docstrings  flake8  linter  git-hook  mypy  unittest  pytest  pylint  mock  iterator  generator  logging  tuple  namedtuple  typing  annotation  pyzmq  zmq  msgpack  action  namespace  remap  control2  ros2_control  gdb  qos  tag  plugins  msg  node  zero-copy  shm  tutorial  algorithm  calibration  diff  pid  dev  colcon  colcon_cd  rpi  arm  qemu  settings  behavior  plot  visualization  debugging  diagnostic  diagnostics  tutorials  gst  math  apm  rat_runtime_monitor  web  rosbridge  vue  binding  discovery  gazebo-classic  launch  spawn  cook  gps  imu  ray  gazebo_ros_ray_sensor  ultrsonic  range  ultrasonic  gazebo classic  wrench  effort  odom  ign  gz  xacro  ros_ign  diff_drive  odometry  joint_state  argument  OpaqueFunction  DeclareLaunchArgument  LaunchConfiguration  tmux  nav  slam  test  rclpy  executor  MultiThreadedExecutor  SingleThreadedExecutor  param  dynamic-reconfigure  service  client  setup.py  package.xml  parameter  parameters  custom  msgs  executers  pub  sub  rqt  rviz  rviz2  pose  marker  tf2  deb  package  setup  local_setup  rosdep  package manager  project settings  vcstool  cross-compiler  nano  texture  tmuxp  rootfs  embedded  zah  linux  rm  ubuntu  ip  ss  network  netstat  snap  deploy  ssh  systemd  mkdocs  extensions  socat  networking  serial  udp  tc  mtu  select  px4  robotics  kalman_filter  kalman  filter  control  todo  vscode-ext  json  yaml  schema  yocto  poky  world  gazebo_ros2_control  position_controller  effort_controller  velocity_controller  urdf  gazebo_ros_force  gazebo_ros_joint_state_publisher  robot_state_publisher  joint_state_publisher  projects  vrx  buoyancy 

Part2 - Launch file

Basic ROS2 launch file

#ros2   #launch   #101  

Table of Content

launch source code#

hello.launch.py
from launch import LaunchDescription
from launch_ros.actions import Node

def generate_launch_description():
    ld = LaunchDescription()

    talker_node = Node(
        package="basic",
        executable="simple_pub",
    )

    listener_node = Node(
        package="basic",
        executable="simple_sub"
    )

    ld.add_action(talker_node)
    ld.add_action(listener_node)

    return ld

Note

Your launch file must contain this function: generate_launch_description(), and must return a LaunchDescription object.

setup.py#

  • Add entry to data_files copy the launch folder to package install folder
setup.py
    data_files=[
        ('share/ament_index/resource_index/packages', ['resource/' + package_name]),
        ('share/' + package_name, ['package.xml']),
        (os.path.join("share", package_name), glob("launch/*.launch.py"))
    ],

Note

copy launch files using CMakeLists.txt 

...

    install(DIRECTORY
    launch
    DESTINATION share/${PROJECT_NAME}
    )

usage#

terminal1
ros2 launch basic hello.launch.py 
# Result
[INFO] [launch]: All log files can be found below /home/user/.ros/log/2022-04-06-08-52-59-435522-lap2-73549
[INFO] [launch]: Default logging verbosity is set to INFO
[INFO] [simple_pub-1]: process started with pid [73551]
[INFO] [simple_sub-2]: process started with pid [73553]
[simple_pub-1] [INFO] [1649224380.693329543] [minimal_publisher]: Publishing: "pub simple: 0"
[simple_sub-2] [INFO] [1649224380.693398516] [minimal_subscriber]: I heard: pub simple: 0
[simple_pub-1] [INFO] [1649224381.683970139] [minimal_publisher]: Publishing: "pub simple: 1"
[simple_sub-2] [INFO] [1649224381.684546630] [minimal_subscriber]: I heard: pub simple: 1

References#